FIELD OF THE INVENTION
The invention lies in the field of electronics. More specifically, the invention relates to an oscillator circuit having a quartz resonator.
U.S. Pat. No. 5,117,206 (see equivalent EP 0 431 887 A2); U.S. Pat. No. 5,446,420 (EP 0 641 080 A2); and U.S. Pat. No. 4,941,156 describe oscillator circuits which include, between a first and a second circuit node, a parallel circuit of a quartz resonator, an inverter and a resistor element. The circuit nodes are each connected to ground via at least one capacitor. At least one of the circuit nodes has a parallel circuit of a sizable number of capacitors which can be switched in or off by means of switches. The frequency of the oscillator circuit can be set in this way.
When the capacitors are switched in or off at arbitrary instants during the operation of the oscillator circuit, the oscillation generated is subjected to an unpredictable influence at the switching instant because of the sudden change in the total capacitance at the respective circuit node.